Physical and Chemical Changes

Think of all the words you can to describe physical changes and come and write them on the board.

What about dissolving?

Think of all the chemical changes you can think of and come and write them on the board.

Chemical Change Something new is produced. The “old” materials are called REACTANTS The “new” materials are called the PRODUCTS Chemical Change

Evidence for Chemical Changes Colour Change Heat, light, or sound produced Heat, light, or sound consumed Bubbles of gas form A precipitate may form Evidence for Chemical Changes

Physical and Chemical Changes Often, physical and chemical changes happen at the same time When you use an explosive to blast rock, gas is produced There is obvious physical changes though too Physical and Chemical Changes

Exothermic Reaction All reactions involve changes in energy! An exothermic reaction RELASES energy in the form of heat or light For example, in a battery, electricity is produced by exothermic chemical reactions…you can feel the heat of a battery! Exothermic Reaction

Enodthermic Reaction All reactions involve changes in energy! An endothermic reaction absorbs energy from the system For example, when you recharge a battery, electrical energy is absorbed by the chemicals in the battery. Enodthermic Reaction

Corrosion Corrosion is a chemical reaction Corrosion involves the breakdown of metals Rust occurs when iron mixes with the oxygen in water. Can you think of any examples when corrosion is good? Corrosion